There are two forms of the past tense – simple past and past participle.
The simple past form is used in the simple past tense whereas the past participle is used in the past perfect tense.

Simple Past – used to talk about actions that are over – I read the book yesterday.

Past Perfect – used to show sequence between two actions in the past – I had read the book by the time he came yesterday.

Apart from the Simple Past and Past Perfect, we also have the Past Continuous and Past Perfect Continuous. Both are used to show that the action is in progress at a given time. For example:

Past Continuous – I was painting at 7 pm the day before.Past Perfect Continuous – I had been painting for 2 hours when the doorbell rang.

While framing a question or negative sentence, the helping verb “do” is changed to the past tense and the main verb remains the same.
For example – Did you call him? I did not have his number.

Now that we have understood the types of verbs and past tense, let’s correct the previous sentences:

“I had sended you the mail.” = “I had sent you the mail.” “Reena forgotted to tell him the update.” = “Reena forgot to tell him the update.” “The team did not worked on this.” = “The team did not work on this.” “Did you went there?” = “Did you go there?”